1. Field of the Invention
The present invention relates to an illumination system for an endoscope including a light source whose brightness is controlled by a control unit and wherein a hook-up cable containing a bundle of optic fibers is provided to transmit light from the light source to a light guide installed in the endoscope and running as far as a distal end of the endoscope.
2. Description of Related Art
Most endoscope applications are in a dark environment, such as the human bladder, and require an illuminating device for diagnostic viewing. As regards the present-day conventional illuminating devices, the light source is very powerful and mounted outside the endoscope. The light source supplies the light to the endoscope through a hook-up cable. Light is supplied to a fiber optics bundle that transmits the light to a light guide installed inside the endoscope. Light is emitted from a distal end of the light guide and illuminates the viewing field adjacent the endoscope distal end.
The cross-sections available in an endoscope are very limited. Accordingly, comparatively thin light guides or fiber optics are used. Since these thin light guides or fiber optics must transmit extremely high light intensities, a number of problems are created.
When endoscopes are interchanged, for instance endoscopes of different length or viewing directions, the hook-up cable typically will be disconnected from an endoscope hookup stub. If, when changing endoscopes, the cable is temporarily laid aside with the light source ON, then the light beam issuing from the end of the hook-up cable, due to its high intensity, may cause damage or even ignite an irradiated material such as a cover cloth.
Moreover, the distal end of the endoscope hook-up cable may be damaged if, with the light source ON, a reflecting or absorbing obstacle is situated directly in front of the end of the fiber optics or light guide. Illustratively absorbent soiling, such as blood in the case of a medical endoscope, may reach the free distal ends of the fiber optics of the hook-up cable or light guide. In this situation, on account of light absorption, strong heating and destruction may ensue.
The patent document WO 98/08430 discloses a light-guide hook-up cable with an integrated electric line and with a sensor situated at its coupling end facing the endoscope. The sensor, in the disconnected state, transmits through the lines a signal to the light source control unit to lower the light intensity of the light source. This feature prevents high-intensity light from issuing from the disconnected end of the hook-up cable. This design, however, incurs the drawback that the remaining problems cited above remain unsolved and creates additional technical problems by requiring additional conductors in the hook-up cable.
The present invention is directed toward a simple and economical solution to the aforementioned problems in the art. The present invention is further directed toward a conventional illumination system that is adapted for the case of a disconnected hook-up cable and also adapted to accommodate the situation wherein the hook-up cable or the light guide on the endoscope side is soiled.
In accordance with the present invention, a light sensor is present at the light-source side end of the fiber optics and looks at at least one fiber. Accordingly, the sensor sees or receives light that is issued by the light source, passes through the fiber optics, and is reflected back at the fiber optics-side end.
If the hook-up cable end is disconnected from the endoscope, the light radiates or projects freely into the ambient as far as distant objects and the fibers reflect only a little of the light. If the hook-up cable is connected to the endoscope, then light will be reflected in the zone of the hook-up fitting and there results a higher, back-reflected light level that can be detected by the sensor. In this manner, the control unit is able to sense and determine whether the hook-up cable is appropriately connected to the endoscope. In the case of a disconnected endoscope, the control unit is able to lower the light source intensity or shut it off in order to minimize damage from emitted light.
Even when the terminal surface of the fiber optics near the endoscope is soiled, the sensor will detect a different back-reflection and will be able to reduce or shut off the light source to prevent destroying the hook-up cable by overheating. If the hook-up cable is connected to the endoscope or, in the case of a bundle of optic fibers, passing through the hook-up cable and installed in the endoscope, the sensor is advantageously used to sense soiling, for instance blood drops, at the distal end of the endoscope or on the end surface of the light guide, in order to minimize the light intensity and to prevent damage or destruction caused thereby.
A single fiber will suffice, in principle, for the purposes of the invention. However, several fibers or even the full bundle of optic fibers may be used for viewing.
The light can be transmitted using a single fiber, several fibers or even the full bundle of optic fibers at the end surface of the bundle near the light sensor. For instance, a light-transmitting corner reflector may be used for transmitting light from the light source to the bundle of fibers. In this procedure, however, the light sensor may be subjected to spurious light from the light source.
In further accordance with the present invention, the fiber or bundle of fibers can be directly coupled to the light sensor while averting spurious light interference. The fiber or fiber bundle used for the back reflection may be integrated into the bundle of fibers of the hook-up cable. Advantageously, however, the fiber or small fiber bundle used for back reflection can be laterally added in a simple manner to the fiber bundle of the hook-up cable after its manufacture. In this manner the end of the fiber or fiber bundle near the light source will exit in a simple manner toward the light sensor. Because the distal fiber end is situated at the edge of the fiber bundle, the edge of the connection site of the hook-up cable and endoscope is especially easily observed and, as a result, reflections at the connection site are easily noted.
The light sensor may be designed to discriminate only with respect to the intensity of the back-reflected light or, also, to sense color. In this manner and, for instance, in the event of blood-drop soiling, the light sensor is able to detect this condition by means of the color and in this dangerous situation it is able to initiate, for instance, an emergency program. Color recognition moreover may be used very advantageously to recognize endoscopes bearing different color codes. Such color codes may be provided in the form of rings of different colors disposed at the hook-up fitting for the hook-up cable. Therefore, the light-source control unit may recognize which particular endoscope is connected. Such recognition may be useful, for instance, for the purpose of correspondingly adjusting the light intensity, to use given filters and the like.